In a video game using a computer, a user generally plays the game by issuing instructions to the character object (hereinafter simply referred to as “character”) operated by the user, by using an input device, so-called controller, that has a plurality of operation keys. When the user presses an operation button on the controller, the game apparatus receives an instruction input signal corresponding to the pressed operation button, and progresses the game by moving the character up or down or left or right or firing a virtual gun, etc. based on the instruction input signal.
Recently, multifunctional controllers that can measure positions and accelerations have become popular. Patent Literature 1 discloses a controller that has a pressure sensor that detects a pressure of pressing an operation button. According to this technique, a game apparatus can detect that an operation button of the controller is pressed, and can also obtain the intensity of the user's pressing the operation button via the pressure sensor.
Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. 2004-33371